1. Field of the Invention
The present invention relates to an electrostatic chuck (hereinafter, “ESC”), and more particularly, to an ESC with an improved combining structure, having a guide ring and an ESC main body to enhance uniformity of deposition and/or etching in a semiconductor manufacturing process.
2. Description of the Related Art
Semiconductor elements are produced by applying various processes to materials. Examples of such processes include a deposition process, an etching process, and a cleaning process. Each process is performed in a chamber that needs to maintain a controlled work environment.
These chambers are often equipped with chucks to hold objects such as wafers. The chucks can be mechanical, vacuum, or electrostatic.
Mechanical chucks stabilize wafers on a supporting surface by using mechanical holders. Mechanical chucks have a disadvantage in that they often cause distortion of wafers due to non-uniform forces being applied to the wafers. Thus, wafers are often chipped or otherwise damaged, resulting in a lower yield.
Vacuum chucks operate by lowering the pressure between the wafer and the chuck below that of the chamber, thereby holding the wafer. Although the force applied by vacuum chucks is more uniform than that applied by mechanical chucks, pressures in the chamber during semiconductor manufacturing processes are non-uniform. Because of the variable chamber pressure, proper force applied cannot be in some situations. In other situations, the pressure in the chamber is too low to perform a vacuum chucking operation.
ESCs, which are gaining popularity, stabilize and hold wafers utilizing a voltage difference between the wafers and electrodes. ESCs apply a more uniform force than mechanical chucks or vacuum chucks.
In an ESC, the chucking of a wafer is achieved using the Coulomb force and the Johnsen-Rahbek effect generated when a voltage-applied dielectric material is charged and its electrodes are polarized. The Johnsen-Rahbek effect is a force generated when a gap is formed by surface irregularities between a wafer and a dielectric material. The gap can be likened to a vacuum for dielectric material. The gap is charged and polarized by current generated when voltage is applied thereto. The ESC can perform heat processing uniformly and minimize generation of particles by attaching the wafer to an ESC main body. Recently, ESCs have been used to hold wafers in a process chamber for chemical and/or physical deposition apparatuses, as well as etching apparatuses.
FIG. 1 is a sectional view of a reaction device having a conventional ESC.
As shown in FIG. 1, the reaction device has an ESC in a sealed reaction chamber 5. The ESC is supported by a supporter 7. The reaction chamber 5 provides a sealed space to form an atmosphere for an object 101 to be processed.
Outside of the reaction device, a reaction gas source 3 is provided to supply the reaction gas. The reaction gas source 3 supplies the reaction gas for deposition or etching to be performed during the semiconductor manufacturing processing.
A media gas supplier 50 supplies a media gas to mediate heat transmission and cool down the ESC main body 130.
The ESC comprises an ESC main body 130; an object 101 disposed on the ESC main body 130; a guide ring 110 to guide the object 101; a voltage supplier 75 to supply voltage to the ESC main body 130; and an RF generator 70 to supply RF power.
FIG. 2 and FIG. 3 are sectional views of the ESC main body of a conventional ESC, and the ESC main body of a conventional ESC with an additional dielectric material layer added.
The ESC main body 130 is made of a metal such as aluminum. The ESC main body 130 has a voltage supplied to it by the voltage supplier 75. When voltage is supplied, the ESC acts as an electrode.
A dielectric material layer 120 in the ESC main body 130 generates an electric charge between the dielectric material layer 120 and the ESC main body 130 when voltage is supplied from the voltage supplier 75. Thus the object 101 is chucked on the upper side of the dielectric material layer 120. The thinner the dielectric material layer 120 is, the greater the electric charge. The electric charge is directly proportional to the square root of a value divided by the thickness of the dielectric material layer 120. The dielectric material layer 120 may be made of materials that include: Al2O3, SiO2, AlN, and the like.
As shown in FIG. 3, the conventional ESC main body with a dielectric material layer 120 has an electrode 135 on top of a first dielectric material layer 120a and a second dielectric material layer 120b on top of the electrode 135. The voltage supplier 75 applies voltage to the electrode 135 so that the object 101 is chucked on the second dielectric material layer 120b. 
The object 101 is disposed on the dielectric material layer 120b. In the semiconductor manufacturing processing, the object 101 is a reaction object of the reaction gas and is usually a plate-type wafer. A pattern or a PR (photoresist) is formed in the object 101.
The RF (Radio Frequency) generator 70 supplies the RF power to the ESC main body 130 to form a desirable reaction gas, and the reaction gas formed therein collides with the object 101 of the ESC main body 130.
The temperature of the object 101 is elevated when the reaction gas collides with the object 101. If the temperature of object 101 is elevated during the semiconductor manufacturing processing, the pattern or the PR formed therein can be damaged, and thus the semiconductor element cannot be produced. Therefore, the heated object 101 has to be cooled.
To lower the temperature of the object 101 that was elevated during the semiconductor manufacturing process, the media gas supplier 50 supplies a media gas 55 to transfer heat from the object 101 to the ESC main body 130. Inside of the ESC main body 130, a media gas hole 160 is provided to transmit the media gas 55 to the bottom side of the object 101.
The amount of the media gas 55 injected can be controlled by a gas valve 45 in the media gas hole 160.
The media gas 55 transfers heat from the object 101 to the ESC main body 130. Helium gas or argon gas is used as the media gas 55 for efficiency of heat transfer.
The ESC main body 130 receives the heat transferred by the media gas 55 and the temperature of the ESC main body 130 is increased. The ESC main body 130 utilizes a coolant fluid therein for cooling. The coolant fluid circulates in the ESC main body 130 through coolant passages 180 provided therein. After absorbing the heat from the ESC main body 130, the coolant fluid returns to a coolant supplier (not shown). The circulation of the coolant fluid cools the ESC main body 130.
The guide ring 110 is provided on the ESC main body 130, or in a groove formed thereon. The guide ring 110 encircles the object 101 and guides it. When the guide ring 110 is exposed to the reaction gas with the object 101, the temperature of guide ring 110 is increased during the semiconductor manufacturing process.
The object 101, heated during the semiconductor manufacturing process can be cooled by allowing media gas 55 to contact the bottom side of the heated object 101 through the media gas hole 160 in the ESC main body 130, thereby transferring heat from the object 101 to the ESC main body 130.
In FIGS. 2 and 3, the media gas 55 contacts the bottom of the heated objected 101 and cools the object 101 only by transferring the heat absorbed from the object 101 to the ESC main body 130.
While the media gas 55 cools the heated object 101, the guide ring 110 is not cooled. As a result, a temperature difference develops between the heated object 101 and the guide ring 110. As the temperature difference becomes greater, the heat from the guide ring 110 is transferred to the outer edge of the object 101, thereby causing the object to have a non-uniform temperature in that the edge will heat up, while the center remains cooler. Such a temperature difference can cause the edge and the center of the object 101 to be processed unevenly during a semiconductor manufacturing process such as etching or deposition, thereby reducing the yield of the object 101.